As a method for producing nitrous acid ester in which nitric oxide, oxygen, and an alcohol are reacted, a method is known in which an alcohol is supplied to the upper part of a reaction column, is made to flow downward from the upper part to the lower part of the reaction column, nitric oxide and oxygen, or a gas mixture thereof is supplied to the lower part of the reaction column, nitric oxide, oxygen, and the alcohol are reacted so as to generate nitrous acid ester, and nitrous acid ester is extracted from the top part of the reaction column (refer to Patent Literature 1 and 2).
In addition, another method is known in which a bottom liquid is extracted from the bottom part of a reaction column, and the bottom liquid is supplied to a reactor for nitric acid conversion, and is brought into contact with carbon monoxide and nitric oxide in the reactor for nitric acid conversion, thereby generating nitrous acid ester (refer to Patent Literatures 3 and 4).